Data communication networks have become increasingly popular. Data communication networks may include various computers, servers, nodes, routers, switches, hubs, proxies, and other devices coupled to and configured to pass data to one another. These devices are referred to herein as “network elements,” and may provide a variety of network resources on a network. Data is communicated through data communication networks by passing protocol data units (such as packets, cells, frames, or segments) between the network elements over communication links on the network. A particular protocol data unit may be handled by multiple network elements and cross multiple communication links as it travels between its source and its destination over the network. Hosts such as computers, telephones, cellular telephones, Personal Digital Assistants, tablets and other types of consumer electronics connect to and transmit/receive data over the communication network and, hence, are users of the communication services offered by the communication network.
Network elements (e.g. Access Points, Mobility Switches and Edge Switches) are typically implemented to have a control plane that controls operation of the network element and a data plane that handles traffic flowing through the network. The data plane typically will have a collection of line cards having ports that connect to links on the network. Data is received at a particular port, switched within the data plane, and output at one or more other ports onto other links on the network. The packets are transferred across the network in accordance with a particular protocol, such as the Internet Protocol (IP).
One type of network is known as a Shortest Path Bridging (SPB) network. SPB technology provides logical Ethernet networks on native Ethernet infrastructures using a link state protocol to advertise both topology and logical network membership. Packets are encapsulated at the edge either in MAC-in-MAC 802.1 ah or tagged 802.1Q/802.1ad frames and transported only to other members of the logical network. Unicast and multicast is supported and all routing is on symmetric shortest paths. Many equal cost shortest paths are supported.
Typically a packet enters an SPB transport network from a user network through a network device referred to as a Backbone Edge Bridge (BEB). The BEB functionality required for Layer 3 (L3) Virtual Services Network (VSN) requires the following operations. On the User to Network (UNI) ingress: the lookup of a Virtual Routing Destination Identifier, Internet Protocol Destination Address (VRD_ID, IP_DA) result points to a Media Access Control (MAC)-In-MAC encapsulation header that is added to the packet and sent into the SPB network. On the terminating Network to Network Interface (NNI) Ingress a lookup of the Service Instance Identifier (I-SID)→Virtual Routing and Forwarding Identifier (VRF_ID); and lookup (VRF_ID, IP_DA) to forward to determine which UNI to forward the packet out of. This is a fairly straightforward implementation on the flexible forwarding hardware that is used in network systems.